1. Field of the Invention
The present invention generally relates to a process for preparing a fluorine-containing hydrocarbon compound such as hydrofluorocarbons (HFC).
2. Description of the Related Art
Fluorine-containing hydrocarbon compounds such as hydrofluorocarbons (HFC) are used as substitute compounds of chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFC) which having a strong action of depleting an ozone layer, and are important compounds used as blowing agents, coolants, cleaners or propellant which do not deplete ozone in the current industry.
It has already been known to use an antimony compound as a catalyst in the process for preparing a hydrofluorocarbon. For example, Japanese Patent Kokai Publication No. 169829/1991 discloses a process for preparing CF3CHCl2, CF3CHCIF or CF3CHF2 by fluorinating CClF2CHCl2 without directly using hydrogen fluoride. Japanese Patent Kokoku Publication No. 91202/1995 discloses a process for preparing CF3CHCl2 by fluorinating CClF2CHCl2 or CCl2FCHCl2, and WO96/01797 discloses a process for preparing 1,1,1,3,3-pentafluoropropane by fluorinating 1,1,1,3,3-pentachloropropane with hydrogen fluoride in the presence of an antimony halide compound.
Although it is known that the antimony halide compound is a highly corrosive compound, none of the patent publications mentioned above refers to corrosion of a reaction apparatus or prevention of such corrosion of a reaction apparatus. According to the description of examples of these publications, the concentration of the antimony halide compound used as a catalyst is usually within a range from about 0.1 to 10 mol based on 100 mol of hydrogen fluoride, and is within a range from about 20 to 30 mol at most. However, the inventors of the present invention confirmed that, when using the antimony halide compound having a concentration within such a range as the catalyst, it exhibits a metallic corrosion action in a very high level.
As described in Japanese Patent Kokai Publication No. 169829/1991, when the fluorination is conducted only by using a fluorine atom-containing antimony halide compound in the absence of hydrogen fluoride in the system, an operation of refluorinating the consumed antimony halide compound and an apparatus therefor are required. Therefore, the process can not be said to be economically advantageous.
WO98/33754 discloses a process for fluorinating 1,1,1,3,3,3-hexachloropropane in a solvent of 1-chloro-1,1,3,3,3-pentachloropropane or 1,1,1,3,3,3-hexafluoropropane and Japanese Patent Kokai Publication No. 217704/1996 discloses a process for simultaneously fluorinating dichloromethane and 1,1,1-trichloroethane, respectively, and these publications describe that the objective compound can be obtained in a good yield and that the corrosion prevention effect of the reaction apparatus is also achieved.
However, as described in WO98/33754, the process using the product or the intermediate product as the solvent is not deemed to be economically advantageous because the volume of a reaction vessel should be increased corresponding to the increase of the amount of the solvent to be used. Furthermore, since some compound has poor compatibility with hydrogen fluoride, phase separation between the hydrogen fluoride and the solvent is likely to occur in the reaction vessel, thereby to drastically lower the reaction efficiency. Therefore, such a process is applicable to limited cases.
The process of simultaneously fluorinating dichloromethane and 1,1,1-trichloroethane described in Japanese Patent Kokai Publication No. 217704/1996 is economically disadvantageous because when any one product is required, the other product which is not necessary is prepared.
In WO98/33754 and Japanese Patent Kokai Publication No. 217704/1996, although the amount of the antimony halide compound based on hydrogen fluoride is not specifically prescribed, the amount is several mol % at most as described in examples of the former publication and there is not an example wherein the antimony halide compound is used in a high concentration. On the other hand, the latter publication describes that, since the temperature of the reaction vessel is maintained at a temperature higher than a boiling point of hydrogen fluoride under a reaction pressure, hydrogen fluoride does not exist in a liquid state in the reaction vessel. That is, this description shows that the concentration of the antimony halide compound is nearly 100 mol % based on hydrogen fluoride. The absence of hydrogen fluoride in the reaction solution is not suited to efficiently conduct the reaction because the feed of a fluorine source in the fluorination reaction is delayed.
As the corrosion-proof fluorination process, Japanese Patent Kokai Publication No. 233102/1995 discloses a process using a reaction vessel made of a fluororesin and Japanese Patent Kokoku Publication No. 88591/1995 discloses a process for lowering the corrosiveness by maintaining a water content in a raw material at a low level, respectively. However, it is not possible to provide an equipment comprising a resin-lined instrument with a heating equipment in the process using the reaction vessel made of the fluororesin described in Japanese Patent Kokai Publication No. 233102/1995 as described in the specification thereof, so that it is difficult to control the reaction temperature. In addition, the raw material is fed in a gaseous form and, therefore, a pre-heater of the raw material is required, resulting in high equipment cost. The process for maintaining the water content in the raw material at a low level described in Japanese Patent Kokoku Publication No. 88591/1995 is not deemed to be economical because dehydration of an organic material requires addition of a dehydrating agent and distillation and also dehydration of hydrogen fluoride requires electrolysis and addition of a fluorine gas, resulting in increase of the number of the steps.
It has hitherto been known that a hydrogen fluoride solution of SbClpF5xe2x88x92p has very high corrosiveness and the reactivity of the hydrogen fluoride solution of SbClpF5xe2x88x92p with respect to the reaction of fluorinating the organic material increases with the increase in concentration thereof. The commonly used concentration was within a range from 1 to 10 mol %, as disclosed in examples of WO96/01797, in view of the economical efficiency.
However, the present inventors found that, when using SbClpF5xe2x88x92p in a concentration, which is comparatively higher than that has hitherto been used, the corrosiveness of SbClpF5xe2x88x92p is lowered within a conventionally used concentration range by the same degree as in the case of a comparatively low concentration range, or a concentration lower than a lower limit in the conventionally used range. Consequently, the present invention has been completed.
An object of the present invention is to provide a process for preparing a fluorine-containing halogenated hydrocarbon compound (HFC), which is important as a substitute or an alternative compound of CFC or HCFC, economically advantageously with good selectivity while suppressing a corrosive action of a reaction vessel.
The inventors have intensively studied to achieve the object described above and devised the present invention which provides a process capable of suppressing the corrosion of a reaction vessel made of a metal while maintaining a high fluorinating ability of an antimony halide compound by using a mixture of hydrogen fluoride and an antimony halide compound, which mixture contains the antimony halide compound in a comparatively high concentration. The above mixture of the antimony halide compound and hydrogen fluoride may also be expressed that it exists in the form of a hydrogen fluoride solution containing an antimony halide compound in a high concentration at normal temperature under normal pressure.
In an aspect, the process for preparing a fluorine-containing halogenated hydrocarbon compound of the present invention is characterized by fluorinating, in a reaction field where an antimony halide compound represented by the general formula:
SbClpF5xe2x88x92pxe2x80x83xe2x80x83(I)
wherein p is a value within a range from 0 to 2, and hydrogen fluoride and a halogenated hydrocarbon compound as a raw material exist, the halogenated hydrocarbon compound in a molar ratio of the antimony halide compound to hydrogen fluoride within a range from 40/60 to 90/10, thereby to prepare a fluorine-containing halogenated hydrocarbon compound.
Particularly, the fluorine-containing halogenated hydrocarbon compound can be prepared by bringing a mixture containing 40 to 90 mol % of the antimony halide compound and 60 to 10 mol % of hydrogen fluoride into contact with the halogenated hydrocarbon compound.
It can be considered that the antimony halide compound functions as a so-called catalyst in this process. According to the process of the present invention, there can be prepared a fluorine-containing halogenated hydrocarbon compound wherein one or more halogen atoms other than fluorine atoms in the halogenated hydrocarbon compound used as a raw material are substituted with fluorine atoms. In this case, substitutable halogen atoms are, for example, one or more halogen atoms selected from chlorine atom, bromine atom and iodine atom.
In the present invention, as the antimony halide compound represented by the general formula: SbClpF5xe2x88x92p, a single compound can be used, as a matter of course, and there can also be used a mixture (or a composition) of two or more kinds of compounds having the composition represented by the above general formula. Therefore, in the case of the single compound, the value of p is an integer of 0, 1 or 2. When using the composition of two or more kinds of compounds, the value of p is within a range from 0 to 2.
The reason why the value of p was defined as described above in the present invention is based on the following fact that was found out. That is, regarding the antimony halide compound wherein the value of p is not within a range form 0 to 2, the reactivity (conversion ratio, selectivity) with respect to the above fluorination reaction is drastically lower than that of the antimony halide compound wherein the value of p is within a range from 0 to 2.
When using the antimony halide compound wherein the value of p is 3 or more, since such compound has poor reactivity, it becomes necessary to raise the reaction temperature to make up for poor reactivity. However, when the reaction temperature is raised, the reaction of chlorinating an organic material is liable to occur. As a result, antimony atoms of this compound are converted from Sb (V) to Sb (III) in a reduced valence state. Therefore, the reactivity of the fluorination reaction due to the antimony halide compound is further lowered against the intention described above. Therefore, it can be said that the value of p within a range from 0 to 2 is an essential constituent in the compound SbClpF5xe2x88x92p when using it as the catalyst of the fluorination reaction in the present invention.
Specifically, the antimony halide compound (SbClpF5xe2x88x92p), which can be used in the present invention, includes at least one compound selected from the group consisting of SbF5, SbClF4 and SbCl2F3. When any compound among this group is used alone, the value of p is an integer of 0, 1 or 2. There can also be used, as the antimony halide compound in the present invention, a mixture (composition) which is obtained by mixing SbCl5 with SbF5 in a predetermined ratio and has a composition represented by the general formula: SbClpF5xe2x88x92p. For example, a composition represented by the general formula: SbClpF5xe2x88x92p can be prepared by mixing 0.8 mol of SbF5 with 0.2 mol of SbCl5 and this composition can be used as the antimony halide compound in the present invention. There can also be used, as the antimony halide compound in the present invention, a composition which is prepared by mixing 100 to 60 mol % of SbF5 with SbCl5 as the balance and is represented by the formula:
SbClpF5xe2x88x92p
wherein 0xe2x89xa6pxe2x89xa62. The antimony halide compound in the present invention can also be prepared by an already-known process of reacting SbF5 with HCl, or reacting SbCl5 with HF in a predetermined ratio, or reacting SbF3 with Cl2.
The content of SbClpF5xe2x88x92p in the mixture of the antimony halide compound (SbClpF5xe2x88x92p) and hydrogen fluoride (the concentration of SbClpF5xe2x88x92p in a hydrogen fluoride solution of SbClpF5xe2x88x92p when considered as the hydrogen fluoride solution of SbClpF5xe2x88x92p) is preferably within a range from 40 to 90 mol %, and is more preferably from 50 to 80 mol %.
The reason why the content of SbClpF5xe2x88x92p was defined as described above is based on the following results found out by examining the corrosiveness of SbCl F5xe2x88x92p as a function of the concentration of SbClpF5xe2x88x92p in the hydrogen fluoride solution of SbClpF5xe2x88x92p. That is, when the concentration is within a range from 0 to 0.5 mol %, the corrosiveness is in a low level. When the concentration is within a range from 0.5 to 5 mol %, the corrosiveness is enhanced with the increase of the concentration. When concentration is within a range from 5 to 10 mol %, the corrosiveness exhibits a very high level and reaches maximum. When the concentration exceeds 10 mol % and further increases, the corrosiveness makes a sudden change and tends to be lowered. When the concentration is within a range from 10 to 40 mol %, the corrosiveness is in a comparatively high level but is gradually lowered. When the concentration is 40 mol % or more, the corrosiveness is lowered to a low level by the same degree as in the case of the concentration within a range from 0 to 0.5 mol %.
As described above, although the corrosiveness is comparatively low even when the concentration of SbClpF5xe2x88x92p is 0.5 mol % or less, it can not be said to be practical with respect to the fluorination reaction because of low concentration.
When the concentration of SbClpF5xe2x88x92p in the hydrogen fluoride of SbClpF5xe2x88x92p is lower than 40 mol %, the corrosiveness is rapidly enhanced. Therefore, it is not preferred. On the other hand, when the concentration is higher than 90 mol %, the reaction rate is lowered by the reduction of the fluorine content of the catalyst. Therefore, it is not preferred with respect to the fluorination reaction.
The reaction temperature in the fluorinating reaction of the halogenated hydrocarbon compound in the present invention is preferably within a range from xe2x88x9210 to 150xc2x0 C., and more preferably from 0 to 120xc2x0 C. The pressure of the reaction system is preferably within a range from 0.01 to 5 MPa, and more preferably from 0.1 to 1.2 MP.
In the process of the present invention, the hydrocarbon compound used as a raw material can be represented by the general formula:
CnHxClyFzxe2x80x83xe2x80x83(II)
wherein n is any integer of from 1 to 3,
when n is 1, x is any integer of from 0 to 2, y is any integer of from 1 to 4, z is any integer of from 0 to 2, and x, y and z satisfy the relationship: x+y+z=4,
when n is 2, x is any integer of from 0 to 3, y is any integer of from 1 to 6, z is any integer of from 0 to 3, and x, y and z satisfy the relationship: x+y+z=4 or x+y+z=6, and
when n is 3, x is any integer of from 0 to 3, y is any integer of from 1 to 8, z is any integer of from 0 to 6, and x, y and z satisfy the relationship: x+y+z=6 or x+y+z=8.
When the halogenated hydrocarbon described above is applied to the process of the present invention, there can be obtained a halogenated hydrocarbon compound wherein the number of fluorine atoms in a molecule was increased by the fluorination reaction. The product obtained by the process of the present invention can be represented by the general formula:
CnHxCly-aFz+axe2x80x83xe2x80x83(III)
wherein n is any integer of from 1 to 3,
when n is 1, x is any integer of from 0 to 2, y is any integer of from 1 to 4, z is any integer of from 0 to 3, a is any integer of from 1 to 4, and x, y, z and a satisfy the relationships: x+y+z=4 and yxe2x89xa7a,
when n is 2, x is any integer of from 0 to 3, y is any integer of from 1 to 6, z is any integer of from 0 to 4, a is any integer of from 1 to 6, and x, y, z and a satisfy the relationship: x+y+z=4 or x+y+z=6 and the relationship: yxe2x89xa7a, and
when n is 3, x is any integer of from 0 to 3, y is any integer of from 1 to 8, z is any integer of from 0 to 7, a is any integer of from 1 to 8, and x, y, z and a satisfy the relationship: x+y+z=6 or x+y+z=8 and the relationship: yxe2x89xa7a.
Specifically, when using, as the raw material, at least one halogenated hydrocarbon compound selected from the group consisting of CH2Cl2 and CH2ClF, at least one fluorine-containing halogenated hydrocarbon compound selected from the group consisting of CH2ClF and CH2F2 can be prepared.
When using, as the raw material, one or more halogenated hydrocarbon compounds selected from the group of compounds represented by the molecular formulas: C2Cl4, C2HCl3, C2HCl5, C2HCl4F, C2HCl3F2, C2HCl2F3, C2HClF4, C2H2Cl4, C2H2Cl3F, C2H2Cl2F2 and C2H2ClF3, one or more fluorine-containing halogenated hydrocarbon compounds represented by the molecular formulas: C2HCl4F, C2HCl3F2, C2HCl2F3, C2HClF4, C2HF5, C2H2Cl3F, C2H2Cl2F2, C2H2ClF3 and C2H2F4.
The compound as the raw material represented by the above molecular formula includes, for example, CCl2xe2x95x90CCl2, CHCl2CCl2F, CHCl2CClF2, CHCl2CF3, CHClFCF3, CHClFCCl2F, CHClFCClF2, CHF2CCl2F, CHF2CClF2, CHClxe2x95x90CCl2, CH2ClCCl2F, CH2ClCClF2, CH2ClCF3, CH2FCCl2F and CH2FCClF2, and the fluorine-containing halogenated hydrocarbon compound as the product represented by the above molecular formula includes CHCl2CCl2F, CHCl2CClF2, CHCl2CF3, CHClFCF3, CHClFCCl2F, CHClFCClF2, CHF2CCl2F, CHF2CClF2, CHF2CF3, CH2ClCCl2F, CH2ClCClF2, CH2ClCF3, CH2FCF3, CH2FCCl2F, CH2FCClF2 and CH2FCF3.
When using, as the raw material, at least one compound selected from the group consisting of CCl3CH2CHCl2, CCl2FCH2CHCl2, CClF2CH2CHCl2, CF3CH2CHCl2, CF3CH2CHClF, CCl3CH2CHClF, CCl2FCH2CHClF, CClF2CH2CHClF, CCl3CH2CHF2, CCl2FCH2CHF2, CClF2CH2CHF2, CHCl2CHxe2x95x90CCl2, CHCl2CHxe2x95x90CClF, CHCl2CHxe2x95x90CF2, CHClFCHxe2x95x90CCl2, CHClFCHxe2x95x90CClF, CHClFCHxe2x95x90CF2, CHF2CHxe2x95x90CCl2, CHF2CHxe2x95x90CClF, CCl3CHxe2x95x90CHCl, CCl2FCHxe2x95x90CHCl, CClF2CHxe2x95x90CHCl, CF3CHxe2x95x90CHCl, CCl3CHxe2x95x90CHF, CCl2FCHxe2x95x90CHF and CClF2CHxe2x95x90CHF, at least one fluorine-containing halogenated hydrocarbon compound selected from the group consisting of CCl2FCH2CHCl2, CClF2CH2CHCl2, CF3CH2CHCl2, CF3CH2CHClF, CCl3CH2CHClF, CCl2FCH2CHClF, CClF2CH2CHClF, CCl3CH2CHF2, CCl2FCH2CHF2, CClF2CH2CHF2, CHCl2CHxe2x95x90CClF, CHCl2CHxe2x95x90CF2, CHClFCHxe2x95x90CCl2, CHClFCHxe2x95x90CClF, CHClFCHxe2x95x90CF2, CHF2C Hxe2x95x90CCl2, CHF2CHxe2x95x90CClF, CCl2FCHxe2x95x90CHCl, CClF2CHxe2x95x90CHCl, CF3CHxe2x95x90CHCl, CCl3CHxe2x95x90CHF, CCl2FCHxe2x95x90CHF, CClF2CHxe2x95x90CHF, CF3CH2CHF2, CF3CHxe2x95x90CHF and CHF2CHxe2x95x90CF2 
The examples described above do not limit the halogenated hydrocarbon compound, which can be applied to the process of the present invention, and any hydrocarbon compound which satisfies the conditions represented by the general formula: CnHxClyFz can be applied to the process of the present invention. As a result, a fluorine-containing halogenated hydrocarbon compound represented by the general formula: CnHxClyFz a can be obtained.
In the process of the present invention, the relationship between the antimony halide compound and the raw material, which are introduced into a reaction field and are brought into contact with each other, is as follows. In the case of the batch-wise reaction, it is advantageous to set the feed amount of the halogenated hydrocarbon compound to be substituted so that the applicable amount of F (fluorine atom) being larger than the amount of Cl (chlorine atom) of such halogenated hydrocarbon compound to be substituted. For example, since the amount of F which can be utilized from the system using 8 mol of SbF5 and 2 mol of HF is 18 mol (=16 mol+2 mol), it is required to control the feed amount of the halogenated hydrocarbon compound, wherein the amount of Cl to be substituted is 1 per molecule, to 18 mol or less.
Although the content of fluorine in the antimony halide compound is reduced when the reaction proceeds, the antimony halide compound whose fluorine content was reduced can be regenerated by fluorinating with hydrogen fluoride. When the rate of the reaction of regenerating the antimony halide compound is higher than that of the main reaction (the reaction of fluorinating the halogenated hydrocarbon compound in the present invention), the antimony halide compound can be fluorinated simultaneously with the main reaction during the main reaction in the reaction field of the main reaction. In the case of the continuous reaction, the halogenated hydrocarbon compound is preferably fed so that the fluorination reaction of the antimony halide compound proceeds simultaneously. When the rate of the reaction of regenerating the antimony halide compound is lower than that of the main reaction, the fluorine content of the antimony halide compound is continuously reduced with proceeding of the main component and the reactivity of the antimony halide compound is also lowered. It is also possible to cope with the situation in such a case by separately fluorinating the antimony halide compound, the fluorine content of which was reduced.
Examples of the mode for carrying out the present invention include the followings.
As the first mode, for example, there is such a mode that a predetermined amount of a halogenated hydrocarbon compound is fed to the reaction field containing a mixture of an antimony halide compound and hydrogen fluoride in a ratio defined in the present invention and the fluorination reaction is conducted. In this case, while only the halogenated hydrocarbon compound is fed to the reaction field, the fluorination reaction of the present invention can be preferably carried out as far as the ratio of the antimony halide compound to hydrogen fluoride is within a range defined in the present invention. Therefore, this mode is suited to the case wherein the reaction is conducted batch-wise.
As the second mode, for example, there is such a mode that a predetermined amount of a halogenated hydrocarbon compound and hydrogen fluoride (and a antimony halide compound, if necessary) are fed to the reaction field containing an antimony halide compound and hydrogen fluoride, thereby to control so that the ratio of the antimony halide compound to hydrogen halide is maintained within a preferred range defined in the present invention. In this case, the ratio of the antimony halide compound and hydrogen halide, which exist in the reaction field, can be maintained at a preferred value by feeding or supplementing hydrogen fluoride being consumed with proceeding of the fluorination reaction and feeding or supplementing the antimony halide compound, if necessary. This mode is particularly suited to the system in which the reaction of regenerating the antimony halide compound as the catalyst is conducted simultaneously with the main component by feeding hydrogen fluoride. Therefore, this mode can be applied widely to a middle system between a batch-wise system and a continuous system.
As the third mode, for example, there is such a mode that after a predetermined fluorination reaction according to the first or second mode is conducted, the fluorination reaction is once stopped and hydrogen fluoride is fed to the reaction field thereby to regenerate the antimony halide compound, and then the fluorination reaction in the first or second mode is conducted again. According to this mode, the process of the present invention can be carried out without making the reaction apparatus having the fluorination reaction field to be complicated.
After the fluorination reaction in the first or second mode is conducted, the antimony halide compound, whose fluorine atom content is reduced, is transferred to a separate apparatus for regeneration, where the regeneration reaction of a catalyst compound is conducted, while the fluorination reaction in the first or second can also be conducted in the reaction apparatus having the fluorination reaction field. In this case, although the reaction apparatus becomes slightly complicated, the apparatus can be efficiently utilized by minimizing the time during which the fluorination reaction apparatus can not be used in the main reaction.
Hydrogen chloride produced during the reaction is preferably extracted from the reaction vessel. The product can be extracted during the reaction or after the completion of the reaction.
As described above, the reaction of the present invention can be conducted batch-wise or continuously. Even when using any system, the reaction product can be separated and recovered by subjecting the effluent obtained from the fluorination reaction to a suitable treatment of distillation, partition, or extraction and separation while contacting with an extractant. While the example of using the halogenated hydrocarbon compound containing only chlorine atoms as the raw material is given in the above description, the process of the present invention is not limited the example and can be applied to any case wherein the halogenated hydrocarbon compound as the raw material contains one, two or three kinds selected from the group consisting of chlorine atom, bromine atom and iodine atom. As a result, a fluorine-containing halogenated hydrocarbon compound containing a larger amount of fluorine atoms can be obtained.
As the material of the reaction apparatus, which can be used in the present invention, so-called nickel alloys containing Ni as a main component, for example, Ni, Nixe2x80x94Mo, Nixe2x80x94Cr, Nixe2x80x94Cu, Nixe2x80x94Crxe2x80x94Mo and Nixe2x80x94Crxe2x80x94Moxe2x80x94Fexe2x80x94Cu alloys are preferred. Preferred examples of these alloys include alloys having the following trade names: Monel 400 (JIS NCuP), Monel 500 (JIS NCUATP), Hastelloy B-2 (JIS NM2P), Hastelloy C-22, Hastelloy C-276 (JIS NMCrP), Hastelloy G (JIS NCrFMCu1P), Inconel 600 (JIS NCF600), Inconel 625 (JIS NCF625) and Inconel 825 (JIS NCF825). Depending on the reaction temperature, a stainless steel (for example, JIS Symbol SUS 304L or SUS 316L), copper and a copper alloy can also be used.
According to the present invention, by fluorinating, in the reaction field where an antimony halide compound represented by the general formula:
SbClpF5xe2x88x92pxe2x80x83xe2x80x83(I)
wherein p is a value within a range from 0 to 2, and hydrogen fluoride and a halogenated hydrocarbon compound as a raw material exist, the halogenated hydrocarbon compound in a molar ratio of the antimony halide compound to hydrogen fluoride within a range from 40/60 to 90/10, a fluorine-containing halogenated hydrocarbon compound can be prepared with good selectivity in good yield as shown in Table 1 and, furthermore, the corrosiveness to a metal can be reduced to a low level as shown in Table 2 to Table 4.